Checkmk

Checkmk leans on a large library of built-in plugins to monitor physical, virtual, containerized, and cloud environments. Rather than asking you to script every check, it ships hundreds of official and community plugins that already know how to read common services, so onboarding a host means installing an agent or pointing at an endpoint. It is built to scale with low resource use.

Monitoring works agent-based or agentless. A web UI drives dashboards, distributed monitoring spreads load across sites, and agent management is automated. Enterprise editions layer on Kubernetes, AWS, Azure, and GCP coverage plus OpenTelemetry metrics, push agents, and host auto-registration, with LDAP and REST API integrations throughout.

The Community edition is free under GPL v2. Linux packages ship as DEB and RPM, every edition runs in Docker, paid tiers come as appliances, and Checkmk Cloud is the SaaS option.